Let me start by saying my DSD is fantastic, an absolute sunshine in a dark sky and I love her. We have a great relationship.
My issue isn't with her it's with DP's parenting. It makes me worry for our future and the support I would get if we ever have children together.
Firstly, DSD has to sit in front of the car and DP refuses to budge and doesn't understand why I think this is unacceptable. It's a total non issue to him. I have to sit in the back of my own car sometimes. If I sit in the front, the whole journey is "why aren't I sitting in the front?" And DP responds "princesses sit in the back, darling"
Every time he goes to the shop, he has to buy her something. I think hang on, how do ever reward her or buy her a genuine treat when it's now becoming expected?
She's five and she decides whether she is staying with us overnight or whether she goes home. If she doesn't get to go home she screams for hours, literally hours. Even if she's been laughing her head off previously, as soon as it's bed time, she decides to go home and DP has to drive her back or her mum come to collect her and cancel clients at home.
He will give her a thousand options over every little thing, she can be screaming because she doesn't want to go to bed and DP says "who would you like to brush your hair baby?" And I'm sat there thinking, she is absolutely knackered and working herself up. Take the lead and just brush her hair?
"DSD, what would you like for dinner" and DD chooses and then says she doesn't like this dinner anymore. Followed by DP saying how about Jam on toast? 
DSD is very confident and will argue with adults, I'll say "the grass is green" and she will argue till she's blue in face. He just laughs his head off.
I love DSD, we get on great and I keep my mouth shut about these issues but his parenting style worries me.